1. Field of the Invention
This invention relates to a process for producing colored shaped articles, particularly a process for producing excellent, colored contact lenses.
2. Description of the Prior Art
Contact lenses are used for correcting poor eyesight, and in usual, colorless and transparent ones are on the market. However, colored contact lenses have been desired for the correction of color blindness, for facial beauty, for prevention of dazzlement in strong sunlight, protection of eyes against ultraviolet light, etc.
In order to satisfy such requirements, there have heretofore been proposed a process for producing a colored contact lens by dissolving or dispersing a dye or a pigment in a monomer and then polymerizing the monomer, and a process for producing a colored contact lens by printing or coating a colored layer onto the surface of a contact lens.
However, contact lenses obtained by these coloring methods tend to undergo discoloration or fading owing to oozing-out of the dye while being used. Particularly, water-absorbent soft contact lenses are disadvantageous in that the dye oozes out owing to the required sterilization of the lenses by boiling or with a cold sterilizing solution, so that the lenses are liable to undergo discoloration.
Therefore, a need still exists for a process for producing a uniformly colored shaped article which undergoes minor discoloration or fading due to oozing-out of the coloring dye.